Grounding is the most misunderstood aspect of electrical distribution. Conventional grounding methods for variable frequency drives (VFDs) are insufficient and can cause issues. High frequency ground currents produced by VFDs using IGBT technology can travel through ground grids, cause motor and electronic equipment damage, and disrupt nearby systems if not properly contained. Zero Ground's HFES system is a passive grounding solution that creates a continuous low impedance path to safely contain these ground currents and prevent issues, requiring no maintenance over the long-term.

1. FACT:
Grounding is the most
misunderstood aspect of
Electrical Distribution

2. Current Flow to Physical Earth
in a Typical VFD Cell using
i T i l VFD C ll i
conventional grounding
• POWER SUPPLY
• DRIVE *typically utilizes IGBT technology
• MOTOR
• WIRING SYSTEM ( MOST NEGLECTED COMPONENT)
WIRING SYSTEM ( MOST NEGLECTED COMPONENT)
Conventional input cabling Conventional output cabling
Drive Frame ( V F D ) *
Transformer Case Frame Motor Frame
OUTPUT
Stator
INPUT
Windings
PE PE PE
I f-g = high
g PE
frequency PE PE
ground I f-g I f-g I f-g
currents
Oscilloscope reads approximately
PE NEC.Sect.250 PCC 1,500 illi
1 500 milliamps going t ground
i to d
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3. Fast switching power devices utilizing
IGBT technology produce electrical interference
(High Frequency Ground Currents,
Bearing Currents, Shaft Currents, ) which
)
C B
Cannot Be Can Be
Can Be
Eliminated Contained
Controlled Redirected
R di t d
ONLY By using Zero Ground HFES
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©2008-2011 ZERO GROUND page 3

4. Issues resulting from High Frequency
Ground Current flow in a typical VFD cell
…Will enter ground grid and travel in all
…Will enter ground grid and travel in all
directions, with arcing, sparking and
shocking as potential safety concerns
…Can discharge through the motor, causing
d h h h h
premature motor bearing failure, which
causes premature motor failure.
…Can re‐enter ground paths through the
ground and disrupt sensitive electronic
equipment and adjacent drive systems
equipment and adjacent drive systems
…This HF ground current flow is the basis for
recommended output cable distance limitation
of 50 feet by most ASD manufacturers
f 50 f b ASD f
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5. High Frequency Ground Current Path - Motors
Red Capacitive coupling b t
R d–C iti li between stator and rotor
t t d t
Green – Inductive coupling through bearings to earth
Colored lines show the various paths High Frequency Ground Currents take
through the motor (bearings, shaft, etc)
when a VFD and motor are grounded conventionally to Physical Earth (PE)
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©2008-2011 ZERO GROUND page 5

6. HFES Creates the
Preferred Grounding Path
f d d h
Unlike other VFD Cable Systems (used only on output side), only Zero Ground HFES is designed and
rated to be used on the input and output side of the Drive. Also unlike traditional VFD cabling, HFES is
a completely passive system, and can be used wherever greater than 50 ft. lengths are required.
Our HFES Flexible Cable Assembly takes conventional Drive System wiring materials and combines
them in a unique and patented design to create a continuous preferred grounding path. That is how
HFES Contains, Controls and Redirects High Frequency Ground Currents and other nuisance noise
AWAY from physical earth (ground). Industry
standard
Inner Component Outer Component fitting
NOTE: Inner Component is inserted into
Outer Component when shipped
Patents have been issued for
UL listed components and cable assembly
p y ZERO GROUND HFES
Components and I t ll ti
C t d Installation
MSHA approved cable assembly Method
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©2008-2011 ZERO GROUND page 6

7. ZERO GROUND HFES
ZERO GROUND
ZERO GROUND HFES
Application Summary
A system of passive wiring components
Low engineered to a specific drive cell
engineered to a specific drive cell
Voltage
(1000V) Patented flexible cable assembly and
patented installation method, for
500 HP
500 HP retrofit or new drive cells
retrofit or new drive cells
or less
INPUT and Fully compliant with NEC 250 and CSA
OUTPUT Section 10
g
wiring
system Not designed to resolve all issues
associated with drives and motors
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©2008-2011 ZERO GROUND page 7

8. HFES delivers continuous ROI –
Why ZERO GROUND HFES is your best
Why ZERO GROUND HFES is your best
long‐term solution
Measurable hi h f
M bl high frequency ground currents are always present in a Drive
d t l ti D i
System, with the potential to create safety issues, induce premature
motor bearing failure and disrupt sensitive devices and systems on
the same or adjacent grounding grids.
the same or adjacent grounding grids
‐‐‐Enables upfront planning for prevention instead of funding ongoing
maintenance and unplanned downtime recovery
‐‐‐No regular maintenance required
No regular maintenance required
‐‐‐No active components to complicate your system
‐‐‐No frequency dependent components (like filters)
‐‐‐No routinely replaceable components (like brushes)
‐‐‐No distance limitations with HFES (cable assembly runs can be moved
or extended as needed)
www.zero-ground.com 866-ZERO-GND
©2008-2011 ZERO GROUND page 8